Boiler Water Problems
Scaling || Corrosion || Carryover
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As water is heated and converted into steam,
contaminants brought into a boiler with makeup water
are left behind. The boiler functions as a
distillation unit, taking pure water out as steam, and
leaving behind concentrated minerals and other
contaminants in the boiler. Scale forms as a result of
the precipitation of normally soluble solids that
become insoluble as temperature increases. Some
examples of boiler scale are calcium carbonate,
calcium sulfate, and calcium silicate.
Corrosion is a general term that indicates the
conversion of a metal into a soluble compound. In
the case of boiler metal, corrosion is the
conversion of steel into rust. In a boiler, two
types of corrosion are prevalent: 1.) Oxygen pitting
corrosion, seen on the tubes and in the preboiler
section. 2.) Low pH corrosion, seen in the
condensate return system. Corrosion of either type
can lead to failure of critical parts of the boiler
system, deposition of corrosion products in critical
heat exchange areas, and overall efficiency loss.
Carryover is caused by either priming or foaming.
Priming is the sudden violent eruption of boiler
water which is carried along with steam out of the
boiler, usually caused by mechanical conditions.
Priming can cause deposits in and around the main
steam header valve in a short period of time.
Foaming causes carryover by forming a stable froth
on the boiler water, which is then carried out with
the steam. Over a period of time, deposits due to
foaming can completely plug a steam or condensate
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